This invention relates to a solar heat selective absorbing material that absorbs solar energy efficiently and having a minimum loss by thermal radiation, and more particularly to a solar heat selective absorbing material prepared by forming a film of a material whose main component is a carbide of a transition metal belonging to the IV group of periodic table on the surface of a substrate, and to a method of manufacturing said material.
Recently, techniques of utilizing solar energy attract attention of those who are in the art and developments of thermoelectric power generation system using selective absorption films are in progress.
The radiation spectrum of sun is such that its peak is present in the vicinity of 0.5 .mu.m, and over 95% of total energy is contained between 0.3 to 2.0 .mu.m. For this reason, as quality of a material that selectively absorbs solar heat. A material must have high absorption in a wavelength region of 0.3 2.0 .mu.m, and also, rate of radiation of heat is small in an infrared region of more than 2.0 .mu.m.
Heretofore, a material of multifilm group such as a metal-dielectric multilayer film or semiconductor reflection preventive film has been developed as a solar heat selective absorbing surface.
The solar heat selective absorbing surface of the multifilm group is involved with a complicated process of forming the film so that a method of using a single material is effective for the simple formation of the film.
As the single material having excellent heat resistance property, carbon has heretofore been known, and also, recently, carbides of metals and the like which are advantageous in view of the heat resistance property are employed.
However, these materials have problems that cannot be sufficiently satisfied with respect to the performances. Accordingly, so far the solar heat selective absorbing material having satisfactory performance which is prepared by a simple method using the conventional film material has not been developed.